Transportation in the United States emitted 4.8 million tons of nitrogen oxides (NOx) in 2023. Since 2006, NOx emissions from transportation have fallen by more than 70 percent. Nitrogen oxides are a group of gases that include nitrogen dioxide. The U.S. Clean Air Act aims to improve air quality by limiting these harmful emissions.
Road vehicle emissions in the U.S.
On-road vehicles contributed to 52 percent of transportation-related NOx emissions in the U.S. in 2023. These vehicles – which include light-duty passenger vehicles, heavy-duty trucks and buses, and motorcycles – are also major contributors to fine particulate matter pollution in the North American country. Tiny particles like PM2.5 can be harmful to human health in high concentrations.
Passenger car emissions
In addition to being a significant source of air pollutants, passenger cars are also major greenhouse gas emitters. Passenger cars are responsible for more than 20 percent of transportation sector greenhouse gas emissions in the United States.
Nitrogen oxides (NOx) emissions from the transportation sector in the United States from 1990 to 2023
(in 1,000 metric tons)
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Environmental Protection Agency. (February 9, 2024). Nitrogen oxides (NOx) emissions from the transportation sector in the United States from 1990 to 2023 (in 1,000 metric tons) [Graph]. In Statista. Retrieved November 01, 2024, from https://www.statista.com/statistics/860125/us-transportation-sector-nox-emissions/
Environmental Protection Agency. "Nitrogen oxides (NOx) emissions from the transportation sector in the United States from 1990 to 2023 (in 1,000 metric tons)." Chart. February 9, 2024. Statista. Accessed November 01, 2024. https://www.statista.com/statistics/860125/us-transportation-sector-nox-emissions/
Environmental Protection Agency. (2024). Nitrogen oxides (NOx) emissions from the transportation sector in the United States from 1990 to 2023 (in 1,000 metric tons). Statista. Statista Inc.. Accessed: November 01, 2024. https://www.statista.com/statistics/860125/us-transportation-sector-nox-emissions/
Environmental Protection Agency. "Nitrogen Oxides (Nox) Emissions from The Transportation Sector in The United States from 1990 to 2023 (in 1,000 Metric Tons)." Statista, Statista Inc., 9 Feb 2024, https://www.statista.com/statistics/860125/us-transportation-sector-nox-emissions/
Environmental Protection Agency, Nitrogen oxides (NOx) emissions from the transportation sector in the United States from 1990 to 2023 (in 1,000 metric tons) Statista, https://www.statista.com/statistics/860125/us-transportation-sector-nox-emissions/ (last visited November 01, 2024)
Nitrogen oxides (NOx) emissions from the transportation sector in the United States from 1990 to 2023 (in 1,000 metric tons) [Graph], Environmental Protection Agency, February 9, 2024. [Online]. Available: https://www.statista.com/statistics/860125/us-transportation-sector-nox-emissions/